Shock-absorbing joint and spine replacements

ABSTRACT

Numerous joint replacement implant embodiments including a total knee replacement implant including a femoral component ( 102 ) having a wheel ( 104 ); and a tibial component ( 106 ) including a shock-adsorbing component with a piston assembly ( 110 ) and spring ( 112 ). Said implants contain a cushioning or shock-absorbing member to dampen axial loads and other forces. In many embodiments, fluid is force rapidly from the device wherein compression and dampening is achieved by valves or other pathways that allow for a slower return of the fluid back into the implant as the pressure is relieved.

FIELD OF THE INVENTION

This invention relates generally to prosthetic implants and, moreparticularly, to artificial disc and joint replacement componentsincorporating shock absorbers, cushioning mechanisms, and otherimprovements.

BACKGROUND OF THE INVENTION

Premature or accelerated disc degeneration is known as degenerative discdisease. A large portion of patients suffering from chronic low backpain are thought to have this condition. As the disc degenerates, thenucleus and annulus functions are compromised. The nucleus becomesthinner and less able to handle compression loads. The annulus fibersbecome redundant as the nucleus shrinks. The redundant annular fibersare less effective in controlling vertebral motion. The disc pathologycan result in: 1) bulging of the annulus into the spinal cord or nerves;2) narrowing of the space between the vertebra where the nerves exit; 3)tears of the annulus as abnormal loads are transmitted to the annulusand the annulus is subjected to excessive motion between vertebra; and4) disc herniation or extrusion of the nucleus through complete annulartears.

Current surgical treatments of disc degeneration are destructive. Onegroup of procedures removes the nucleus or a portion of the nucleus;lumbar discectomy falls in this category. A second group of proceduresdestroy nuclear material; Chymopapin (an enzyme) injection, laserdiscectomy, and thermal therapy (heat treatment to denature proteins)fall in this category. A third group, spinal fusion procedures eitherremove the disc or the disc's function by connecting two or morevertebra together with bone. These destructive procedures lead toacceleration of disc degeneration. The first two groups of procedurescompromise the treated disc. Fusion procedures transmit additionalstress to the adjacent discs. The additional stress results in prematuredisc degeneration of the adjacent discs.

Prosthetic disc replacement offers many advantages. The prosthetic discattempts to eliminate a patient's pain while preserving the disc'sfunction. Current prosthetic disc implants, however, either replace thenucleus or the nucleus and the annulus. Both types of current proceduresremove the degenerated disc component to allow room for the prostheticcomponent. Although the use of resilient materials has been proposed,the need remains for further improvements in the way in which prostheticcomponents are incorporated into the disc space, and in materials toensure strength and longevity. Such improvements are necessary, sincethe prosthesis may be subjected to 100,000,000 compression cycles overthe life of the implant.

The same is true of total joint replacements, which must endure repeatedcompressive stresses associated with daily activities such as walking,running, exercising, sitting and standing. These compressive stressescan eventually cause painful fractures and can often result in theimplant loosening after several years. Ultimately, revision surgery maybecome necessary.

Prosthetic implants that address impact problems are known in the art.For example, U.S. Pat. No. 5,389,107 to Nassar et al. discloses aprosthetic hip implant having an elongate element that extends coaxiallyfrom the ball section of the femur component. The elongate elementslidably extends into a chamber formed by a tubular insert that issecured in the femur. Contained at the bottom of the chamber is a springagainst which the elongate element abuts, thereby providing shockabsorption. A pin member extends from the bottom of the chamber andslidably fits into a bore formed in the elongate element. A secondspring is disposed between the pin and the bottom of the bore to providefurther shock absorption.

U.S. Pat. No. 6,336,941 discloses a modular hip implant that can becustom fit to an individual patient, including a shock absorption systemthat absorbs compressive stresses that are imparted to the implant. Thesize of the femoral ball member, size of the femoral stem, femoral necklength, and tension in the shock absorption system are all individuallyadjustable parameters, depending on the particular patient. A uniquecoupling member houses a modular spring mechanism that serves as theshock absorber. The coupling member is received into the ball member toan adjustable depth, the adjustment of which varies the length of thefemoral neck. The length of the femoral neck can be adjusted duringsurgery without requiring additional parts.

This invention is broadly directed to spine and joint-replacementcomponents wherein, in preferred embodiments, at least a portion of therespective implant contains a cushioning or shock-absorbing member. Suchmembers, which serve to dampen axial loads and other forces, need not becontained entirely within the joint or disc space, as it may beadvantageous according to the invention to provide devices external tothe region of direct articulation.

In many embodiments, fluid is forced rapidly from the device withcompression, and dampening is achieved by valves of other pathways thatallow for a slower the return of the fluid back into the device as thepressure is relieved. In intradiscal configurations, spinal motionoccurs by movement of the vertebrae over the device, and by the devicechanging shape. Various fluids may be used within the device includingwater or aqueous solutions, triglyceride oil, soybean oil, an inorganicoil (e.g. silicone or fluorocarbon), glycerin, ethylene glycol, or otheranimal, vegetable, synthetic oil, or combinations thereof. Fluids fromthe body, such as synovial fluid, may also move into and out of unsealeddevice components.

In some embodiments, transplanted cells and/or cells plus theextracellular matrix (ECM) or analogues thereof, may be contained in thedevice. For example, a fluid permeable: fiber bag, carcass as describedin my U.S. Pat. No. 6,419,704, or a cylinder or other enclosures asdescribed in my pending U.S. Patent Application Ser. No. 60/379,462 maybe used to hold the cells or the cells and ECM within the disc space orelsewhere in the body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an anterior view of a total knee replacement (TKR) accordingto the present invention;

FIG. 2 is a lateral view of the TKR of FIG. 1;

FIG. 3 is drawing of a total hip (THR) embodiment of the presentinvention;

FIG. 4 shows the use of a membrane used to contain metal or otherdebris;

FIG. 5 is a cross section of the embodiment of FIG. 4;

FIG. 6 is an axial cross section through the top of the device of FIG.4;

FIG. 7A is a lateral view of an acetabular component according to theinvention;

FIG. 7B is lateral view of the acetabular component of FIG. 7A;

FIG. 8 is a sagittal cross section of the device of FIG. 7A;

FIG. 9A is coronal cross section of another embodiment of the presentinvention;

FIG. 9B is a coronal cross section of the embodiment of the device drawnin FIG. 9A;

FIG. 10A is a partial coronal cross section of a prosthetic kneeincluding a dampening mechanism; and

FIG. 10B is a partial coronal cross section of the prosthetic knee drawnin FIG. 10A;

FIG. 11 is a lateral view of the spine and a device according to thepresent invention;

FIG. 12 is an anterior view of the spine and the device of FIG. 11;

FIG. 13 is an axial view of the spine and the device of FIG. 11;

FIG. 14 is a sagittal cross-section of the device of FIG. 11;

FIG. 15 shows an exploded view of the device of FIG. 11;

FIG. 16 is a sagittal cross section of another embodiment of the presentinvention;

FIG. 17 shows an exploded view of the device of FIG. 16;

FIG. 18 is a view of the lateral portion of the spine and an embodimentwith endplate resurfacing components;

FIG. 19 is a view of the anterior portion of the spine and the device ofFIG. 18:

FIG. 20 is top view of a three-cylinder embodiment of the presentinvention;

FIG. 21 is a sagittal cross section of the device of FIG. 20;

FIG. 22 is a sagittal cross section of an embodiment having a singlepiston;

FIG. 23 illustrates compression of the piston of the device of FIG. 22;

FIG. 24 is an exploded view of the device of FIG. 22;

FIG. 25 is a view of the anterior portion of the device with alow-pressure reservoir;

FIG. 26 is a lateral view of the of FIG. 25;

FIG. 27 is a view inside the device of FIG. 25 the outer membrane incross section;

FIG. 28 is a full cross section of the device of FIG. 25;

FIG. 29A is a lateral view of a compressed device according to theinvention;

FIG. 29B is a lateral view of the device drawn in FIG. 29A after thecompression is relieved;

FIG. 30A is a lateral view of a device with a hinge associated with atop endplate;

FIG. 30B is a lateral view of the device with the hinged portion of theupper endplate tilted forward as in spinal flexion;

FIG. 31A is a partial coronal cross section of the spine and anotherembodiment of the invention;

FIG. 31B is a partial coronal cross section of the embodiment of thedevice drawn in FIG. 31A;

FIG. 32 is an anterior view of an alternative embodiment of an ADRaccording to the invention;

FIG. 33 is a coronal cross-section of the spine and the embodiment of adevice particularly suited to the L4/L5 level and above;

FIG. 34 is a lateral view of the spine and the embodiment of the devicedrawn in FIG. 33;

FIG. 35 is an anterior view of the spine, sacrum, and the embodiment ofthe device drawn in FIG. 33;

FIG. 36 is a sagittal cross section of the spine, sacrum, and theembodiment of the device shown in FIG. 35;

FIG. 37 is a coronal cross section of the spine incorporating a slightvariation of the device drawn in FIG. 33;

FIG. 38 is a lateral view of the spine and the embodiment of the devicedrawn in FIG. 37;

FIG. 39 is a coronal cross section of the spine incorporating a furtheralternative embodiment of invention;

FIG. 40 is a lateral view of the spine including the embodiment of thedevice drawn in FIG. 39;

FIG. 41A is a coronal cross section of the spine and yet a furtherembodiment of the device made of a material with shape memory;

FIG. 41B is a coronal cross section of the spine and the embodiment ofthe device drawn in FIG. 41A;

FIG. 42 is a coronal cross section of the spine and yet a differentembodiment of the present invention;

FIG. 43A is a view of the anterior portion of the spine and anotherdifferent embodiment of the invention;

FIG. 43B is a coronal cross section of the spine and the embodiment ofthe device drawn in FIG. 43A;

FIG. 44 is a coronal cross section of the spine and another furtherembodiment of the invention;

FIG. 45A is a coronal cross section of the spine and yet a differentembodiment of the invention;

FIG. 45B is a coronal cross section of the spine and the embodiment ofthe device drawn in FIG. 45A;

FIG. 46A is a coronal cross section of an alternative embodiment of thepresent invention;

FIG. 46B is a coronal cross section of the embodiment of the ADR drawnin FIG. 46A;

FIG. 47 is a coronal cross section of an alternative embodiment of anADR according to the invention;

FIG. 48 is a coronal cross section of the embodiment of the ADR drawn inFIG. 47;

FIG. 49 is a sagittal cross section of a total knee replacementincorporating a device according to this invention;

FIG. 50 is a sagittal cross section of the total hip replacementembodiment of the device of the present invention;

FIG. 51A is a sagittal cross section of a disc embodiment according tothe invention;

FIG. 51B is a sagittal cross section an alternative disc embodiment; and

FIG. 52 is a sagittal cross section of an alternative disc embodiment ofthe invention.

DETAILED DESCRIPTION OF THE INVENTION

This invention is broadly directed to spine and joint-replacementcomponents wherein, in preferred embodiments, at least a portion of therespective implant contains a cushioning or shock-absorbing member. FIG.1 is an anterior view of a total knee replacement (TKR) according to theinvention. FIG. 2 is a lateral view of the TKR of FIG. 1. The femoralcomponent, 102, includes a wheel 104. The tibial component, 106,includes one or more shock-absorbing components, such as piston assembly110 and one or more springs such as 112 which may be separate from orsurround each piston assembly. The spring on the left in FIG. 1 was notdrawn to better illustrate the cylinder halves. An optional membrane 120may surround the tibial shock absorbers to hold in fluid and/orparticulates such as metal debris. The natural synovial fluid within theknee joint may be used to advantage to cooperate with the dampeningmechanism.

FIG. 3 is a total hip (THR) embodiment of the invention. As with theknee, a membrane 302 may be used to contain fluid and/or debris. The THRcould also work on synovial fluid if the membrane were torn oreliminated.

FIG. 4 is an alternative THR embodiment with a membrane 402 and a flapvalve 404 below the spring. The expandable membrane surrounding the topof the implant also holds the fluid that is forced through the flapvalve. As a further option, the femoral component may contain a spacefor the inferior membrane to expand into. The inferior space 406 couldbe closed or contain a hole to communicate with the canal of the femur.Distention of the inferior membrane would compress the air surroundingthe membrane. The compressed air would help form the fluid into the areasurrounding the spring when tile pressure is decreased.

FIG. 5 is a cross section of an alternative embodiment of the inventionincluding a modular, removable shock absorber component 502. FIG. 6 isan axial cross section through the top of the device. Not that the neckof the shock absorber component cooperates with the femoral stemcomponent to prohibit rotation of the one component relative to theother. As in other embodiments, the modular component, contains fluid, aspring and cylinder halves. The femoral stem component has an openingthat allows the fluid-containing membrane 504 to expand. A secondmembrane (not shown) may extend from the base of the (Morse) taper ofthe shock absorber component to the top of the femoral stem component.The second membrane would contain particle debris generated by pistoningof the shock absorber component within the femoral stem component.

FIG. 7A is a lateral view of an acetabular component according to theinvention which includes slidably engageable components that extend fromthe acetabular component to prevent dislocation. The movable componentsresist forces perpendicular to the components while reliably collapsinginto the acetabular component with axial forces. The posterior movablecomponent resists posterior dislocation of the femoral component. Theanterior moveable components collapse in the position shown in FIG. 7Ato prevent levering the femoral component out of place.

FIG. 7B is lateral view of the novel acetabulum component of FIG. 7A,with the THR extended. The posterior movable component collapses and theanterior movable components extend in this position of the THR. FIG. 8is a sagittal cross section of the device. The movable components pistonin and out of cylinders in the acetabular component. Springs force themovable components partially out of the acetabular component.

As discussed in the Background of the Invention, in these and in otherembodiments, the sealed, fluid containing components may contain wateror aqueous solutions, triglyceride oil, soybean oil, an inorganic oil(e.g. silicone or fluorocarbon), glycerin, ethylene glycol, or otheranimal, vegetable, synthetic oil, or combinations thereof.Alternatively, fluids from the body, such as synovial fluid could moveinto and out of unsealed embodiments of the device. Indeed, certainconfigurations according to the invention may use both a sealed fluidand the body's fluid, with seals to prevent the sealed fluid fromcommunicating with the fluid from the body. Pores in a portion of theprosthesis may be sized to permit fluid movement, but to inhibit bone orsoft tissue ingrowth into the chamber in the inferior portion of theprosthesis. Wave washers or other spring-like components could be usedto force the prosthetic component(s) into an extended, non-compressedposition. The stiffness of the spring or springs could vary. Stiffersprings could be selected for heavier or more active patients.

FIG. 9A is coronal cross section of an embodiment including a dampeningmechanism associated with a prosthetic hip. A component 902 preferablyincluding a Morse taper pistons in and out of the shaft of theprosthesis. An optional membrane 904 serves to trap debris. Thecomponent with the Morse taper may have the anti-rotation features drawnin FIGS. 5 & 6. A piston extending from the inferior surface of theMorse taper component is surrounded by one or more seals, includingO-rings seals, to trap fluid within the prosthesis. A spring forces theMorse taper component into an extended, resting, position. A valve suchas a flap valve lies below the ledge in the prosthesis that holds thespring. A piston surrounded by seals lies below the valve in a cylinderwithin the shaft of the prosthesis. A component with pores is seen atthe inferior entrance into the cylinder in the inferior aspect of theprosthesis. Fluid moves from the sealed chamber above the valve to thesealed chamber below the valve as pressure is applied to the Morse tapercomponent.

FIG. 9B is a coronal cross section of the embodiment of the device drawnin FIG. 9A. The figure illustrates movement of the components in areaction to pressure on the top of the Morse taper component. The Morsetaper component moves inferiorly, within the shaft of the prosthesis, aspressure is applied to the top of the Morse taper component. Fluidwithin the upper chamber of the prosthesis is forced through and aroundthe flap valve into the lower chamber as the Morse taper movesinferiorly. The lower piston moves distally within the lower chamber toaccommodate the additional fluid. Body fluid below the inferior pistonis forced through the porous component and into the shaft of the femuras the inferior piston moves distally. The components of the prosthesisreturn to the positions shown in FIG. 9A when the pressure is removedfrom the top of the Morse taper component. The flap valve slows thefluids return to the upper chamber thus dampening the movement acrossthe prosthesis. Fluid from the femur moves into the chamber in theinferior portion of the prosthesis as the inferior piston rises as thesealed fluid moves to the upper chamber.

FIG. 10A is a partial coronal cross section of a prosthetic knee withthe novel dampening mechanism illustrated in FIG. 9. The components aredrawn in their “extended” position. FIG. 10B is a partial coronal crosssection of the prosthetic knee drawn in FIG. 10A. The components aredrawn in their “compressed” position. The figure also illustrates theuse of an optional expandable membrane used to trap debris within theprosthesis. The figure also illustrates the use of additional springs.

Different aspects of this invention are directed to artificial discreplacement (ADR) devices that use shock absorbers to dampen axial loadsacross the disc space. Fluid is forced rapidly from the device withcompression. Dampening of the axial forces is achieved by valves ofother pathways that slow the return of the fluid back into the device asthe pressure is relieved. Spinal motion occurs by movement of thevertebrae over the device, and by the device changing shape.

FIG. 11 is a lateral view of the spine and a device according to theinvention in position. FIG. 12 is an anterior view, FIG. 13 is an axialview, and FIG. 14 is a sagittal cross-section. Pistons 1102 are housedin cylinders 1104. Springs force the pistons out of the cylinder. Thisembodiment also shows the optional use of ball bearings 1106 in thepistons. The ball bearings may reduce the friction of the device on thevertebral endplates.

FIG. 15 is an exploded view of the device. The circles 1502 in the bodyof the device represent valves such as flap valves. The valves allowfluid to leave the device with compression, faster than they allow fluidto return to the device as the compression is relieved. In the preferredembodiment, the device uses natural body fluid. For example, naturallubricant like fluid is frequently found in the joints found inpsuedoarthrosis. Similarly, the body frequently manufactures lubricantlike fluid to decrease friction between prosthetic devices and overlyingsoft tissues. In this embodiment the fluid lies freely in and around thedevice. FIG. 25 shows another embodiment with a fluid containing lowpressure reservoir just outside the disc space.

FIG. 16 is a sagittal cross section of another embodiment of the devicewhich incorporates ball bearings on the inferior surface and in thecylinders of the device. FIG. 17 is an exploded view of the device ofFIG. 16. FIG. 18 is a view of the lateral portion of the spine and anembodiment with endplate resurfacing components 1802, 1804. Thecompressible portion of the device is free to move and self-centerbetween the two endplate resurfacing components. The endplateresurfacing components can cooperate to prevent the extrusion of themobile, compressible member.

FIG. 19 is a view of the anterior portion of the spine and the device ofFIG. 18. FIG. 20 is top view of a three-cylinder embodiment that allowslarger pistons, fewer parts, and further exploits the ability of athree-legged structure such as a three-legged stool, to fit veryirregular surfaces. FIG. 21 is a sagittal cross section of the device ofFIG. 20, also showing an embodiment of the pistons without ballbearings. FIG. 22 is a sagittal cross section of an embodiment having asingle piston. FIG. 23 illustrates compression of the piston of thedevice of FIG. 22. FIG. 24 is an exploded view of the device of FIG. 22.FIG. 25 is a view of the anterior portion of the device with a lowpressure reservoir (cross hatched area) that sits just outside the discspace.

The advantages of theses embodiments include the following:

1. Durability. Springs, pistons, cylinders and ball bearings haveexcellent wear characteristics.

2. The device dampens forces across the disc space. Most ADR designsallow spinal motion. Some ADR designs collapse and expand to accommodatecompression forces across the disc space. Few ADR designs dampen axialforces across the disc space.

3. The fluid that moves into and out of the device not only providesdampening of the forces across the disc spaces but also lubricates themoving components of the device.

4. The springs of the device are contained within cylinders to maximizespring function and to prevent the springs from migrating.

5. The compressible portion of the device is mobile to allow the deviceto self center.

6. The mobile portion of the device is tethered to prevent migrationinto undesirable locations.

7. The embodiments with ball bearings may reduce the friction betweenthe device and the vertebral endplates.

8. The endplate resurfacing components may decrease the risk of painfrom movement of the device over the endplates of the vertebrae.

9. Multi-piston embodiments of the device permit the device to “customfit” the concavities of the vertebral endplates. The pistons may extendvariable distances above this device.

10. The pistons of the multi-piston embodiments of are unlikely to bind.The piston of a single piston device is more likely to bind.

11. Self-centering. One or more components may be attached to a mobilelink that allows the ADR to self-center. The device may also be placedbetween the resurfacing components described above.

FIG. 26 is a lateral view of an alternative ADR including an expandablemembrane 2602 that holds fluid within the device. FIG. 27 is a viewinside the device with the outer membrane in cross section, and FIG. 28is a full cross section. A spring surrounds a fluid-filled cylinder. Theupper half of the cylinder pistons in and out of the lower half-of thecylinder. Fluid is forced through holes in the upper half of thecylinder with compression of the device. The fluid egresses rapidly atfirst, through the large holes in the upper half of the cylinder. Thefluid exits more slowly as the larger holes in the upper half of thecylinder become covered by the lower half of the cylinder. The fluidthat leaves the cylinder is contained within the device by thesurrounding membrane. Fluid returns to the cylinder as the device isexpanded by the spring urging the cylinder halves apart. Fluid returnsto the cylinder slowly at first through the smaller holes exposedinitially by the lower half of the cylinder (thus dampening the motionof the device). As the device expands the larger holes in the upper halfof the cylinder are exposed, thereby allowing the fluid to return to thecylinder more quickly.

FIG. 29A is a lateral view of the device in a compressed condition. Theouter membrane is drawn in cross section without the spring to betterillustrate operation. Note that the outer membrane is protruding outwardas a result of the endplates becoming closer together and from the fluidmoving from the cylinder. FIG. 29B is a lateral view of the device drawnin FIG. 29A after the compression is relieved. FIG. 30A is a lateralview of the device with a hinge associated with the top endplate. Thehinge facilitates flexion and ex-tension. The vertebrae are free to moveover the device. Tilting of the top endplate allows the vertebrae toflex and extend more with less movement over the device. The upperhinged potion is preferably bi-convex to allow lateral bending. FIG. 30Bis a lateral view of the device with the hinged portion of the upperendplate tilted forward as in spinal flexion.

The advantages of theses embodiments include the following:

1. Durability. Springs, pistons, and cylinders have excellent wearcharacteristics.

2. The device dampens forces across the disc space. Most ADR designsallow spinal motion. Some ADR designs collapse and expand to accommodatecompression forces across tile disc space. Few A-DR designs dampen axialforces across the disc space.

3. The fluid that moves into and out of the device not only providesdampening of the forces across the disc space, but also lubricates themoving components of the device.

4. Fewer parts compared to other designs.

5. The compressible portion of the device is mobile to allow the deviceto self center.

6. The mobile portion of the device is tethered to prevent migrationinto undesirable locations.

7. The embodiment with the hinged endplate component may reduce thefriction between the device and the vertebral endplates.

8. The endplate resurfacing components may decrease the risk of pain dueto movement of the device over the endplates of the vertebrae.

As with the joint-replacement embodiments, the fluid containingembodiments may contain water or aqueous solutions, triglyceride oil,soybean oil, an inorganic oil (e.g. silicone or fluorocarbon), glycerin,ethylene glycol, or other animal, vegetable, synthetic oil, orcombinations thereof. Alternatively, the expandable membrane of FIGS.26-31B could be eliminated, allowing fluid from the body to freely moveinto and out of the ADR.

Wave washers, belville washers, belville springs, or other spring-likecomponents could be used to force the ADR to an extended, non-compressedposition. The stiffness of the spring or springs could vary. Stiffersprings could be selected for heavier or more active patients.

The extradiscal portion of the device preferably includes a porouscomponent that allows the body fluid to move in and out of theextradiscal component as the sealed fluid moves in and out of theextradiscal component. The pores are sized to permit fluid movement, butto inhibit bone or soft tissue growth into the chamber of theextradiscal component.

FIG. 31A is a partial coronal cross section of the spine and anotherembodiment of the device. The bottom of the shock absorbing component isattached to the vertebra below the ADR. The top of the shock absorbingcomponent articulates with an ADR Endplate (EP) that is attached to thesuperior vertebra. The springs are seen in cross section.

FIG. 31B is a partial coronal cross section of the embodiment of thedevice drawn in FIG. 31A. The springs were not drawn to betterillustrate the inside of the ADR. The figure also illustrates the use ofan optional seal between the articulation of the inner cylinder and theouter cylinder. For example, an 0-ring could surround the innercylinder.

FIG. 32 is an anterior view of an alternative embodiment of the ADR. Theembodiment of the ADR drawn in FIG. 31 is connected to an extradiscalcomponent. The outer membrane is preferably flexible, but does not needto be expandable in this embodiment of the device.

Where an extradiscal component is used in conjunction with anintradiscal component, the pressure within the intradiscal component ofthe device increases as axial loads are applied to the spine or thespine flexes. In operation, fluid within the intradiscal component ofthe device shifts to the lower pressure extradiscal component as thepressure on the intradiscal component increases. Fluid returns to theintradiscal component of the device as the pressure on the intradiscalcomponent is decreased. Pressure on the intradiscal component isdecreased by removing the axial loads on the spine or by returning thespine to a neutral position. The fluid within the relatively highpressure extradiscal component shifts to the lower pressure intradiscalcomponent as the pressure on the intradiscal component decreases. Theextradiscal component may be positioned lateral to the spine in fromT1-L5 and anterior to the sacrum at L5/S1. The extradiscal componentcould also be placed at a remote site. For example, the extradiscalcomponent of a cervical ADR could be placed in the chest, or under theskin of the abdomen.

FIG. 33 is a coronal cross-section of the spine and an embodiment of theinvention particularly suited to the MA/L5 level and above. FIG. 34 is alateral view of the spine and the embodiment of the device drawn in FIG.33. FIG. 35 is an anterior view of the spine, sacrum, and the embodimentof the device drawn in FIG. 33. The embodiment of the device drawn inFIG. 35 is designed for the L5/SI level.

FIG. 36 is a sagittal cross section of the spine, sacrum, and theembodiment of the device shown in FIG. 35. FIG. 37 is a coronal crosssection of the spine incorporating a slight variation of the devicedrawn in FIG. 33, wherein the opening between the intradiscal andextradiscal components is smaller. FIG. 37 also shows the use of a valveto fill the device. FIG. 38 is a lateral view of the spine and theembodiment of the device drawn in FIG. 37.

FIG. 39 is a coronal cross section of the spine incorporating analternative embodiment of the device. The extradiscal component issurrounded by a sleeve that does not expand. FIG. 40 is a lateral viewof the spine including the embodiment of the device drawn in FIG. 39.

The surfaces of each component can be forced from concave to convex orconvex to concave if the appropriate forces are applied. For example,the convex intradiscal component becomes concave with the application ofaxial loads to the spine or spinal flexion. Fluid from the intradiscalportion of the device is shifted to the extradiscal component as theintradiscal component changes from convex to concave. The increasedpressure from the shift of fluids forces the concave extradiscalcomponent to become convex. Once the pressure on the intradiscalcomponent of the device is relieved, the extradiscal component returnsto its convex shape. The extradiscal component returns to its concaveshape. Fluid returns to the intradiscal component as the components ofthe device return to their preferred shapes.

FIG. 41A is a coronal cross section of the spine and yet a furtherembodiment of the device made of a material with shape memory. Thesuperior and/or inferior surfaces of the intradiscal portion of thedevice are preferably convex, whereas the lateral and/or medial surfacesof the extradiscal portion of the device are preferably concave.

FIG. 41B is a coronal cross section of the spine and the embodiment ofthe device drawn in FIG. 41A. In this Figure, the spine is flexed, theintradiscal component of the device has changed to a concave or flatshape, and the extradiscal component of the device is convex.

FIG. 42 is a coronal cross section of the spine and another embodimentof the device. The device can be filled with a fluid and air. The area4202 of the drawing represents fluid. The air in the extradiscalcomponent, being more compressible than liquid, is compressed as fluidmoves from the intradiscal component to the extradiscal component. Thecompressed air forces the fluid to return to the intradiscal componentonce the pressure on the intradiscal component is relieved.

FIG. 43A is a view of the anterior portion of the spine and anotherembodiment of the invention wherein an extradiscal component surrounds aportion of the intradiscal component 4302. The intradiscal extension ofthe extradiscal component helps hold the intradiscal and extradiscalcomponents together. FIG. 43B is a coronal cross section of the spineand the embodiment of the device drawn in FIG. 43A. The intradiscalcomponent is threaded into, or otherwise connected to, the extradiscalcomponent.

FIG. 44 is a coronal cross section of the spine and another embodimentof the invention wherein the intradiscal component is a cylinder with adiaphragm covering a portion of the superior surface of the cylinder.

FIG. 45A is a coronal cross section of the spine and another embodimentof the invention including an expandable extradiscal component. Fluidfrom the intradiscal component forces the two cylinders of theextradiscal component apart. A spring or elastic bands stretches as thecylinders are forced apart. The spring pulls the cylinders of theextradiscal component together forcing the fluid into the intradiscalcomponent once the pressure on the intradiscal component is relieved.Seals are used between the cylinders of the extradiscal component. Avalve is included in the extradiscal component to “bleed” air from thesystem.

FIG. 45B is a coronal cross section of the spine and the embodiment ofthe device drawn in FIG. 45A. FIG. 45B illustrates expansion of theextradiscal component and compression of the intradiscal component withaxial pressure on the spine or flexion of the spine.

In further alternative embodiments, the extradiscal component could besurrounded by a sleeve to help prevent expansion. As a different option,the device may be constructed of metal with spring like shape memory. Inthe embodiment shown in FIG. 41A, the device is made of metal orplastic, and may or may not include a bias-ply, radial, or beltedconstruction.

FIG. 46A is a coronal cross section of an alternative embodiment of theinvention. The upper ADR Endplate (EP) is represented by the area of thedrawing with vertical lines. The upper ADR EP articulates with a secondcomponent 4602. For example the two components could articulate throughgenerally concave and generally convex surfaces. The second componentalso pistons up and down in the lower ADR EP 4604. A spring, or othermechanism such as a wave washer, is used to force the second componentfrom the lower ADR EP.

Seals are preferably used between the second component and the lower ADREP. For example, O-rings could be used between the components. Anextradiscal component is connected to the intradiscal portion of theADR. The extradiscal component contains a piston 4606, seals, and avalve 4608. The intradiscal component and the extradiscal componentscontain fluid that freely follows from one component to the other.

FIG. 46B is a coronal cross section of the embodiment of the ADR drawnin FIG. 46A. The drawing illustrates compression of the intradiscalcomponent. Compression of intradiscal component forces fluid to theextradiscal component. The piston of the extradiscal component moves toallow more fluid to enter the extradiscal component. The ADR componentsreturn to the positions drawn in FIG. 46A as compression is removed fromthe intradiscal component. The spring forces the convex intradiscalcomponent away from the lower ADR EP.

The convex intradiscal component has a mechanism to prevent the convexcomponent from disassociating from the lower ADR EP. A piston withelongated arms from the lower ADR EP is inserted through a slot in thecylinder of the convex component. The convex component is then rotated,to couple the two components together. The valve in the extradiscalcomponent dampens the intradiscal component by forcing the fluid toreturn to the intradiscal component slower than the fluid exited theintradiscal component. A flap valve could be used to slow the fluidsreturn to the intradiscal component. The extradiscal component could bereversibly connected to the intradiscal component to ease the ADRinsertion process. The extradiscal component could lie adjacent to thevertebrae. The cylinder of the extradiscal component has extensions toprevent the piston of the extradiscal component from popping out of theADR.

FIG. 47 is a coronal cross section of an alternative embodiment of theADR according to the invention wherein an extradiscal component iscontained within a vertebra. The drawing also illustrates the use ofmore than one spring and more than one valve. The valves are representedby the area of the drawing with diagonal lines. The piston of theextradiscal component lies within a chamber that projects from the lowerADR EP, into the lower vertebra. The inferior surface of the chamber haspores to allow natural body fluid to more between the chamber and thevertebra as the piston moves with fluid movement between the intradiscaland extradiscal components. The fluid that moves between the intradiscalcomponent and the extradiscal component is sealed within the components.The fluid sealed within the intradiscal and extradiscal components doesnot communicate with the fluid than moves into and out of the chamber inthe lower vertebra. A seal or seals around the piston of the extradiscalcomponents keeps the two fluids separate.

FIG. 48 is a coronal cross section of an alternative embodiment of theADR drawn in FIG. 47. The embodiment of the device drawn in FIG. 48combines the dampening of the invention with the multiple springs andspherical joints taught in my co-pending U.S. patent application Ser.No. 10/434,931 incorporated herein by reference. Fluid from the springand spherical joint components flows into and out of a singleextradiscal component. Multiple extradiscal components could also beused.

As a further option, transplanted cells and/or cells plus theextracellular matrix (ECM) or analogues thereof, may be contained in adevice according to the invention. For example, a fluid permeable bag or‘carcass’ may be used as described in my U.S. Pat. No. 6,419,704,incorporated by reference, or a cylinder or other enclosures asdescribed in my pending U.S. Patent Application Ser. No. 60/379,462,also incorporated by reference, may be used to hold the cells or thecells and ECM within the disc space or elsewhere in the body.

The pores of the device are preferably small enough to prevent cellsfrom leaving or entering the device. Preventing cell migration may helpprevent graft vs. host disease. Nutrients and wastes, however, would befree to move through the pores of the device with fluids. The pores ofthe device could also be large enough for cells to migrate through thepores. The ECM of the transplanted tissue may prevent migration of cellsinto and out of the device.

The device would also enable intervertebral disc cells to betransplanted to other areas of the body. As described in my co-pendingU.S. Patent Application Ser. No. 60/399,597, incorporated herein byreference, the intramedullary canal of long bones and the metaphysis oflong bones may be used support the growth of other, non-native, tissues.For example, a cylinder device filled with intervertebral disc cells andECM, or chondrocytes and ECM could be used to cushion or damperprosthetic joints.

The prosthetic joints could be similar to those disclosed in the pending'597 Application referenced above. Intervertebral disc cells and ECM, aswell as, chondrocytes and ECM could also be used to cushion jointswithout the encapsulating device. The device could also contain stentsto enhance circulation, similar to those described in my pendingco-pending U.S. patent application Ser. No. 10/143,237, furtherincorporated herein by reference.

FIG. 49 is a sagittal cross section of a total knee replacement, andFIG. 50 is a sagittal cross section of a total hip replacement. In theseembodiments of the invention, IVD cells and ECM and/or chondrocytes andECM are represented by the dotted area of the drawing. The articularcomponent of the knee replacement is connected to a piston disposedwithin the cylinder of the device. Cells and cells plus ECM cushion themotion of the knee replacement. The cells and ECM do not necessarilyneed to be contained within a cylinder device. For example, the cellsand ECM could sit directly above a “cement restrictor-like” device.Polymers, gels, fluids, or elastomers could be used in place of thecells and ECM. Cells have the advantage of self-repair. The piston wouldhave holes if fluid is used in a hydraulic-like shock absorber.

FIG. 51A is a sagittal cross section of a disc embodiment of theinvention having superior and inferior endplates that attach to thevertebrae above and below the disc. A flexible membrane 5102 surroundsor encapsulates the disc tissue. Stents (as described in my co-pendingU.S. patent application Ser. No. 10/143,237, incorporated herein byreference) can be seen coursing through the artificial endplates. Thestents allow nutrition and fluid to pass from the vertebrae to the disctissue. The opening into the stents could be small enough to preventcells from migrating into or out of the device. For example, the openingin the stents could be 1-7 micrometers in size. Autograft disc tissueremoved from the disc to allow insertion of the device, could be placedinto the device as described in my co-pending U.S. patent applicationSer. No. 10/120,763, similar to the device described in my co-pendingU.S. patent application Ser. No. 10/434,917, both of which areincorporated herein by reference.

FIG. 51B is a sagittal cross section an alternative disc embodiment ofthe invention. The artificial endplates contain pores to allow fluid tomove into and out of the device. A permeable membrane lies between theartificial endplates and the disc tissue. The holes in the membrane aresized to prevent the migration of cells into or out of the device. Theholes in the artificial endplates can be larger than seven micrometers.FIG. 52 is a sagittal cross section of an alternative disc embodiment ofthe invention. The portion of the device that encapsulates the disctissue articulates with an artificial endplate that attaches to theinferior surface of the superior vertebra.

1. A prosthetic implant configured for placement between opposing bonesthat apply pressure to the implant during articulation, the implantcomprising: a fluid-filled reservoir; and a body coupled to at least oneof the bones and the reservoir to provide cushioning duringarticulation.
 2. The prosthetic implant of claim 1, wherein the body isa piston.
 3. The prosthetic implant of claim 1, wherein the fluid iswater or an aqueous solution.
 4. The prosthetic implant of claim 1,wherein the fluid is a synthetic or naturally occurring oil.
 5. Theprosthetic implant of claim 1, wherein the fluid is an organic orinorganic oil.
 6. The prosthetic implant of claim 1, further includingsuperior and inferior endplates; and wherein the body is coupled to atleast one of the endplates as part of an intervertebral discreplacement.
 7. The prosthetic implant of claim 1, further including aproximal tibial component and a distal femoral component; and whereinthe body is coupled to at least one of the proximal tibial and distalfemoral components as part of a total knee replacement.
 8. Theprosthetic implant of claim 1, further including an acetabular componentand a proximal femoral component; and wherein the body is coupled to atleast one of the acetabular and proximal femoral components as part of atotal hip replacement.
 9. The prosthetic implant of claim 1, furtherincluding a valve or other device that allows the fluid to be expelledfrom the reservoir during the application of the pressure and drawn backinto to the reservoir as the pressure is relieved.
 10. The prostheticimplant of claim 1, wherein the fluid is expelled relatively rapidlyfrom the reservoir during the application of pressure, and drawn backinto the reservoir at a relatively slow rate as the pressure isrelieved.
 11. The prosthetic implant of claim 1, further including oneor more springs to assist in moving the body from the reservoir aspressure is relieved.
 12. The prosthetic implant of claim 1, furtherincluding a membrane to contain debris or particulates.
 13. Theprosthetic implant of claim 1, further including multiple reservoirs,each with a body coupled to one of the bones.
 14. The prosthetic implantof claim 1, further including a wheel or other rolling component tocontrol articulation.
 15. The prosthetic implant of claim 1, furtherincluding a prosthetic femoral head to which the body is coupled. 16.The prosthetic implant of claim 1, wherein the fluid-filled reservoir isassociated with an intramedullary stem.
 17. The prosthetic implant ofclaim 1, wherein: the fluid-filled reservoir is disposed between theopposing bones and further including a second reservoir not disposedbetween the opposing bones; and fluid is transferred from thefluid-filled reservoir to the second reservoir when pressure is appliedand returned to the fluid-filled reservoir when pressure is relieved.18. The prosthetic implant of claim 1, wherein the fluid in thereservoir includes one or more biologic constituents.
 19. The prostheticimplant of claim 18, wherein the biologic constituents includeintervertebral disc cells.
 20. The prosthetic implant of claim 18,wherein the biologic constituents include an extracellular matrix oranalogues thereof.
 21. The prosthetic implant of claim 1, furtherincluding a fluid permeable membrane having pores small enough toprevent cell migration while facilitating the transfer of nutrientsand/or waste materials.
 22. The prosthetic implant of claim 1, whereinthe fluid-filled reservoir or other components may be customized to suita patent's weight or activity level.
 23. The prosthetic implant of claim1, further including a return spring having a stiffness selected to suita patient's weight or activity level.